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Std Model.)

.G. M. HOPKINS.

Telephone" Transmitter.

No. 238,902. Patented March 15,1881.

' WITNESSES:

' ATTORNEYS.

' UNITED STATES PATENT OFFICE.

GEORGE M. HOPKINS, OF BROOKLYN, NEW YORK.

T-ELEPHONE-TRANSM ITTER.

SPECIFICATION forming, part of Letters Patent No. 238,902, dated March15, 1881.

' Application filed November 9, 1880. (No model.)

To all whom it may concern Be it known that I, GEORGE M. HOPKINS, ofBrooklyn, in the county of Kings and State of New York, have invented anew and useful Improvement in Telephone-Transmitters, of which thefollowing is a specification.

My invention consists in the combination of a pendent rocking electrodewith a diaphragm carrying a convex or cylindrical electrode; and itfurther consists in apivoted support for the diaphragm and pendentelectrodes Figure 1 in the drawings is a rear elevation, partly insection, and Fig. 2 is a vertical transverse section taken on line 00 .rin Fig. 1.

Similar letters of reference indicate corresponding parts in the twofigures.

The object of this invention is to avoid delicate adjustments and toprovide a telephonetransmitter that is susceptible to the faintestsounds and is capable of receiving heavier sounds without jarring orrattling.

The diaphragm A is mounted on the back of the mouth-piece B, leaving athin space between the diaphragm aud mouth-piece. A socket, (J, issecured to the center of the diaphragm, and supportsacylindrical carbonpencil, D, parallel with the diaphragm, in a horizontal position. Thejaws of the socket reach a short distance beyond the middle of thecarbon pencil and tend to spring together, and so clamp the carbonpencil. The carbon pencil may be turned in its socket to present a newcontact-surface should occasion require.

A carbon disk, E, is supported by a small spiral spring, F, from abinding-post, Gr, projectin g from the back of the mouth-piece B. Theend of the wire forming the spring is straightened and inserted in thebinding-post. This arrangement admits of adjusting the disk E to anydesired height. Instead of employing the binding-post G, I may attachthe spring F to a lever or screw, or any other suitable adjustingmechanism. The diskE rests against the carbon pencil D, and its centerof gravity is below the line of contact between it and the carbon pencilD. In this arrangement of parts I take advantage of the property ofinertia to prevent the carbon disk E from ever breaking contact with thecarbon pencil D to such an extent as to cause a jar or rattle in thereceiving-telephone. A forward movement of the diaphragm pushes forwardthe upper portion of the carbon disk E, causing it to rock on thecylindrical surface of the carbon pencil D.

The mouth-piece B is pivoted in a box, H, 5 5

on screws a a, which pass through the sides of the box into the edges ofthe mouth-piece at diametrically opposite edges of the diaphragm, and ina line parallel with the carbon pencil D. The screws pass throughmetallic washers b b, which are connected by wires with binding-posts cc in the top of the box H. The screw a enters a metallic nut, cl,inserted in the edge of the mouth-piece B, and the nut d is connected bya wire, 0, with the binding-post G. The screw to enters a metallic nut,01, in the opposite edge of the mouthpiece B, and the nut d is connectedby a wire. 6, with the socket O supporting the carbon pencil D. The backof the box H is closed by a door, I, having an aperture, K, over whichis placed a piece, f, of wire-cloth. The apertured back admitssound-vibrations at the back of the diaphragm and increases the usefuleffect.

The carbon disk E is made to bear with more or less force on the carbonpencil D byinclinin g the mouth-piece B more or less. This is done byloosening the screws to a and turning the n1outh-piece. A tangent-screwor other mechanical device may be used to move the mouthpiece.

This transmitter is connected up in the telephone-circuit in the usualway-that is, the binding-posts c c, are connected with a local circuit,including a battery and the primary wire of an induction-coil, thesecondary wire of the induction-coil being connected with atelephone-line in which are inserted the receiving-telephones.Thelocaloircuitisthrough 0 the carbon disk E and the carbon pencil D,and whenever the diaphragm A is disturbed by sonorous vibrations thecontact between the two carbon surfaces is varied or broken so as toproduce a corresponding disturbance in 5 the electrical condition of thelocal circuit. This induces the secondary current in the small wire ofthe induction-coil, which produces audible effects in the telephoneconnected with it.

Experiment has proven that this transmit- 10o ter will receive andtransmit articulate speech while the speaker is sixty feet distant fromit,

. immediate vicinity of the instrument.

and without any change of adjustment it will transmit speech when thespeaker is in the It has also been shown that the loudest tones producedby the human voice can be transmitted without causing rattling orjarring, and that without change of adjustment it will transmit awhisper. These important advantages are due to the rocking of the carbondisk on the carbon pencil and the consequent avoidance of anyappreciable break in the electrical current.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is

1. In a telephone-transmitter, a rocking pendant consisting of aplane-surfaced disk of material capable of conducting electricity, in

combination with a vibratory cylindricallyconvex electrical conductor,the two electrical 2o conductors being relatively disposed so that theplane surface of the pendent conductor is tangent to the cylindricalsurface of the convex conductor, substantially as specified.

2. In a telephone transmitter, a pendent 25 electrode having its line ofelectrical contact above its center of gravity, as herein specified.

3. In a telephone-transmitter, a pivoted mouth-piece, in combinationwith a diaphragm,

a vibratory electrode, and a pendent electrode, 0 as herein specified.

GEORGE M. HOPKINS.

Witnesses:

H. M. HOPKINS, O. SEDGWICK.

